Method and apparatus for using a discriminative classifier for processing a query

ABSTRACT

A method and apparatus for using a classifier for processing a query are disclosed. For example, the method receives a query from a user, and processes the query to locate one or more documents in accordance with a search engine having a discriminative classifier, wherein the discriminative classifier is trained with a plurality of artificial query examples. The method then presents a result of the processing to the user.

This application is a continuation of U.S. patent application Ser. No.12/347,516, filed Dec. 31, 2008, now U.S. Pat. No. 8,799,279, and isherein incorporated by reference in its entirety.

The present invention relates generally to query processing, and inparticular, to a method and apparatus for using a discriminativeclassifier for processing a query.

BACKGROUND OF THE INVENTION

As the Internet has grown, search engines are relied upon for locatingrelevant information from various repositories located on the World WideWeb (WWW). For example, an Internet user may perform a search byentering a word, a phrase, or a set of keywords into a Web browsersoftware, or a thin client toolbar running on the user's computer. Thesearch engine has a query processor that finds matching informationresources, e.g. web pages, images, documents, videos, and so on. Thesearch engine may then provide one or more matching responses to theuser. Search engines have also become prevalent in Intranets, i.e.,private enterprise networks, where keywords are used by such searchengines to locate documents and files.

The most common algorithms in search engines are based on inverted indexsearch techniques. Inverted index search techniques are fast and canhandle a large number of documents.

However, these techniques lack optimal (well-defined) criteria. Forexample, the search may be for a query with a limited domain. Forexample, the query may be for a specific type of restaurant in aspecific city. When using an inverted index search technique,determining the importance of index terms used for ranking as comparedto the importance of the geographical context is difficult. The indexterms may have different significance in a local context as compared toa global context.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides a method and apparatusfor using a classifier for processing a query. For example, the methodreceives a query from a user, and processes the query to locate one ormore documents in accordance with a search engine having adiscriminative classifier, wherein the discriminative classifier istrained with a plurality of artificial query examples. The method thenpresents a result of the processing to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exemplary network where a discriminativeclassifier is deployed in a network for processing a query;

FIG. 2 illustrates a flowchart for using a discriminative classifier forprocessing a query; and

FIG. 3 illustrates a high level block diagram of a general purposecomputer suitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The present invention broadly discloses a method and apparatus forproviding a local classifier for a network. For example, the localclassifier may be provided in a search engine for a network. When thesearch engine receives a query, the search engine may then performsearches using the local classifier. In order to better describe thepresent invention, the following networking concepts and terminologieswill first be provided:

Information retrieval (IR);

An n-gram;

Support Vector Machine (SVM) classifier.

Logistic regression classifier.

Information retrieval (IR) is the field of searching for information indocuments, searching for documents themselves, searching for metadatawhich describe documents, or searching within databases, whetherrelational stand-alone databases or hypertextually-networked databasessuch as the World Wide Web.

An n-gram refers to a sub-sequence of n items from a given sequence. Forexample, if the sequence is a sequence of words and n is equal to two,the n-gram refers to a sub-sequence of 2 words from the given sequence.For example, if the sequence of words is “The temperature is risingrapidly” and n is equal to two, the sub-sequences are “The temperature”,“temperature is”, “is rising”, and “rising rapidly.”

Support Vector Machine (SVM) classifier refers to a discriminativeclassifier that maximizes separation between two classes using positiveand negative training examples. SVM puts discriminative weights onsearch terms for each class, instead of putting Term Frequency-InverseDocument Frequency (TF-IDF) weights used by traditional search methods.For example, the positive training examples may provide similar weightsto those of TF-IDF while the negative training examples may adddiscriminant negative weights that maximize the separations betweenclasses.

Logistic regression (also known as Maximum Entropy classifier) is amodel used for prediction of the probability of occurrence of an eventby fitting data to a logistic curve, which transforms a continuous scoreinto a probability ranging from 0 to 1. An example is classified aspositive if its logistic score is close to 1, and as negative if itsscore is close to 0. Like SVMs, logistic regression can be viewed as adiscriminant classifier which maximizes separation between classes, withthe same type of weights. The main differences are the trainingalgorithms use to estimate the weights, and the criteria used tominimize the number of non-zero weights (known as regularization).

An information retrieval process begins when a user enters a query intoa computer system that has a search engine, or into a computer that hasaccess to a search engine on another device. Queries are formalstatements of information needs issued to the search engine. The searchengine receives the query and processes the query to locate the desiredinformation. The search engine retrieves information that matches thequery and presents it the user. In order to locate relevant informationin response to a query, the search engine uses n-grams that appear indocuments.

FIG. 1 illustrates an exemplary network where a discriminativeclassifier is deployed in a network for processing a query. The network100 comprises a plurality of endpoint devices 102-104 configured forcommunication with the Internet Protocol over Multi-Protocol LabeledSwitch (IP/MPLS) network 110 (e.g., an IP based core backbone networksupported by a service provider). The endpoint devices 102-104 maycommunicate with the 1P/MPLS core network 110 via an access network 101.Similarly, a plurality of endpoint devices 105-107 are configured forcommunication with the core packet network 110 via an access network108.

The endpoint devices 102-107 may comprise customer endpoint devices suchas telephones, cellular phones, personal computers, laptop computers,Personal Digital Assistants (PDAs), servers, routers, and the like. Theaccess networks 101 and 108 serve as a means to establish a connectionbetween the endpoint devices 102-107 and the Network Elements (NEs) 109and 111. The access networks 101 and 108 may each comprise a DigitalSubscriber Line (DSL) network, a broadband cable access network, a LocalArea Network (LAN), a Wireless Access Network (WAN), a 3^(rd) partynetwork, and the like.

Some NEs (e.g., NEs 109 and 111) reside at the edge of the IP/MPLS coreinfrastructure and interface with customer endpoints over various typesof access networks. An NE that resides at the edge of a coreinfrastructure is typically implemented as an edge router, a mediagateway, a border element, a firewall, a switch, and the like. An NE mayalso reside within the IP network (e.g., NEs 118-120) and may be used asa mail server, a router, or like device. The IP/MPLS core network 110comprises an application server 112 that contains a database 115, BorderElements (BEs) 109 and 111, and routers 118-120. The application server112 may comprise any server or computer that is well known in the art,and the database 115 may be any type of electronic collection of datathat is also well known in the art.

Those skilled in the art will realize that although only six endpointdevices, two access networks, five network elements and one applicationserver are depicted in FIG. 1, the communication system 100 may beexpanded by including any number of endpoint devices, access networks,network elements, 3^(rd) party networks, application servers, etc.without altering the scope of the present invention.

In one embodiment, the current method first presents the search problemin terms of a classification problem. For example, the method may builda profile, or set of features, for each document, or class, to beidentified by a search engine. For example, if queries are beingprocessed to search for a book in a library, each book may be profiledin terms of features like subject, author, title, etc.

The method then provides a scoring algorithm for the search engine,wherein the scoring algorithm is implemented as a discriminativeclassifier. For example, the method may provide a logistic regressionclassifier or an SVM classifier in the application server 112 thatfunctions as a search engine to process queries.

The method then trains the discriminative classifier to distinguish aclass relative to all other local classes. The classifier then createsseparation margin between a class and all other classes. The trainingassigns an optimal weight to each of the features (which correspond tosearch terms) of each class (which corresponds to names or documents).That is, the distance between classes is maximized and the optimalweight is assigned to each term with the goal of uniquely identifyingeach document.

In one embodiment, the method constructs one or more examples fortraining from the names and documents available for each class. In oneembodiment, the one or more examples for performing the training may bederived from logs of previous searches.

For the example above, if the author of a book has a unique name, andthe author has published only one book, the discriminative classifiermay assign more weight to the author's name as opposed to the subject ortitle. On the contrary, if the author has a popular name, e.g., Smith,the author's name may be assigned a small weight, e.g., close to zero.That is, less discriminative terms are given smaller weight.

In one example, the search engine may be used to process queries tolocate a company in a local phone directory. A profile may then be builtfor each entry in the directory such that queries can be processed. Forexample, a profile for a dentist treating children may be built. Usersmay issue queries using a variety of terms e.g., “dental office”,“dentist”, “children's dentist”, “children's health”, etc. Adiscriminative classifier may assign more weight to “children's dentist”as opposed to simply the term “dentist.” Furthermore, the discriminativeclassifier may include assigning a negative weight to the term “doctor”as the term may not be specific enough.

In one example, a discriminative classifier may be used by a searchengine to process a query for XYZ Corporation. That is, the query mayinclude the strings “XYZ” and “Corporation.” “Corporation” is a stringthat is less discriminative as compared to that of “XYZ.” Hence, thediscriminative classifier may assign more weight to the string “XYZ” ascompared to that of the string “Corporation.” Consequently, thedocuments that have “XYZ” in their name should appear prior to documentsthat have “Corporation” in their name.

In one embodiment, the current method provides a discriminativeclassifier for a search engine that may process speech based queries.For example, the outputs from a speech recognition device and/or weightsassociated with words may be used as meta information. The queryreceived via a voice input may include words that have no usefulpurpose, e.g., “umm”, “ah”, “eeh”, “wait”, etc. Speakers may uttersounds freely to a human listener and the listener would normallydisregard the utterances that have no useful purpose. On the contrary,the voice recognition device may pick up every utterance and include thewords in an n-gram regardless of usefulness. The training of thediscriminative classifier (based on profiles built for each document)separates the classes.

The method then receives one or more queries. For example, a search termis received by a search engine. The search engine then processes the oneor more queries to locate the desired information and presents theresult to the user.

In one embodiment, the processing of the query may be based on metainformation, e.g., user profiles, past search results, popularity of alisting, etc. For example, a user may issue a query and the context ofthe query may be understood based on previous search results, userprofile, etc. For example, if previous queries were related to acomputer and the user enters the search term “Apple”, search results forApple computer may be presented as opposed to results related to fruits.

The method then receives feedback on presented results. For example, theuser may click on a link indicating that the result is of interest tothe user. In another example, the user may provide feedback via anindicator of a degree of satisfaction, e.g., yes or no, for the providedresults.

The method may then use the feedback information to retrain thediscriminative classifier. The retraining may update the weightsassigned to search terms. In one embodiment, the method may also retrainthe discriminative classifier based on updates of documents and profilesof documents.

For the example above, if the author who had published only one bookpreviously publishes additional five books, the weight assigned to theauthor's name may then be reduced in favor or assigning more weight toeither the titles of the books or subject matter of each book. That is,optimal weights are assigned to each of the search terms such that eachof the six books from the same author may also be uniquely identified.

FIG. 2 illustrates a flowchart of a method 200 for using adiscriminative classifier for processing a query. For example, one ormore steps of method 200 can be implemented by application server 112.Method 200 starts in step 205 and proceeds to step 210.

In step 210, method 200 provides a scoring algorithm for a search enginein the network, wherein the scoring algorithm is a discriminativeclassifier. For example, the method may provide a logistic regressionclassifier or an SVM classifier.

In step 220, method 200 builds a set of training examples for each ofone or more documents to be identified by the search engine. Forexample, if queries are being processed to search for a book in alibrary, the method may build a profile for each book in terms of itssubject, author, title, etc.

More specifically, training a classifier requires training data. In oneembodiment of the present invention, the training data comprisesartificial query examples. In other words, there is no need to collectand manually label user data. Instead, the present invention creates thequery examples artificially (simulated examples), thereby providingdiscriminant learning that optimizes searches in a way that approximatesuser choices.

For example, for each document, the method may generate a plurality ofartificial examples that comprises typical examples of queries (broadlyreferred to as positive examples) and counter-examples of queries(broadly referred to as negative examples). Assume for an algorithmthat, for each document D* produces a list of example queries Q*:

D1−>(Q1,Q2)

D2−>(Q2,Q3)

Suppose one wishes to build a classifier that provides an answer if aquery should return document D1 or not, then:

positive examples include Q1 and Q2

negative examples include Q3.

More specifically, using a listing B1 (broadly a document), whereB1=[Westfield Gourmet Pizza, 123 Westfield Ave., Westfield, N.J.]. ForB1, the following queries are artificially created: 1. Westfield, 2.Gourmet, 3. Pizza, 4. Westfield Gourmet, 5. Gourmet Pizza, and 6.Westfield Gourmet Pizza. Then, in one embodiment, each query is repeatedwith the street name appended (e.g., appending the street name“Westfield Ave.” to the Query 6 above will produce “Westfield GourmetPizza, Westfield Ave.”), and so on. Furthermore, queries with streetname is further appended with town name (e.g., appending the town name“Westfield” to the Query 6 above will produce “Westfield Gourmet Pizza,Westfield Ave., Westfield”), and so on. It should be noted that theabove six (6) illustrative examples are considered to be positiveexamples.

However, the present invention also automatically creates artificialnegative examples for each listing or document. In one embodiment, all(or a subset of) other artificial positive examples for all otherlistings or documents will be considered to be negative examples.However, if a negative example is identical to a current positiveexample, then the negative example will be considered to be a positiveexample. For example, if there is another listing comprising “ABC pizza”having the artificial queries of “ABC pizza” and “pizza”, then “ABCpizza” is a negative example, whereas “pizza” is still a positiveexample. Furthermore, during the training process, if a particular querycan be generated from more than one listing or document, it is treatedas a multi-label query which can be matched to any of these listings,and can be contrasted to all remaining listings.

In step 230, method 200 trains the discriminative classifier using theset of artificial query examples. The training enables thediscriminative classifier to distinguish a class or a group of similarclasses relative to all other classes. For example, the method performsthe training to assign an optimal weight to each of one or more searchterms associated with each document such that the search engine is ableto uniquely identify each document.

In step 240, method 200 receives one or more queries from a user. Forexample, a user may provide one or more search or query terms to asearch engine.

In step 250, method 200 processes the one or more queries to locate oneor more documents in accordance with the discriminative classifier. Forexample, the method locates the desired information using thediscriminative classifier to uniquely identify documents that best matchthe search terms. The classifier attributes a search score to eachdocument. The documents are then sorted in decreasing order of thisscore. The top N documents in this sorted list may be considered as amatch, or all the documents whose score is above a given threshold maybe considered as a match.

In step 260, method 200 presents the result of the processing to theuser. For example, the method presents one or more documents that matchthe one or more search or query terms.

In optional step 270, method 200 receives a feedback on the resultspresented to the user. For example, the method may receive a feedbackfrom the user in a form of a response (e.g., yes or no) to a questionsuch as “is the search result what you are looking for?”.

In optional step 280, method 200 retrains the discriminative classifierbased on the feedback. For example, the method may retrain thediscriminative classifier such that responses for future queries may beimproved. The method then proceeds to step 290 to end processing thecurrent query, or return to step 240 to continue receiving more queries.

Those skilled in the art would realize that two or more steps of method200 may occur in parallel. As such, the order of the steps in FIG.2 isnot intended to limit the scope of the invention to a specificimplementation. For example, the method may first build the profile foreach document (as described in step 220) prior to providing thediscriminative classifier (as described in step 210). Alternatively,building the profile for each document and providing the discriminativeclassifier may occur concurrently.

It should be noted that although not specifically specified, one or moresteps of method 200 may include a storing, displaying and/or outputtingstep as required for a particular application. In other words, any data,records, fields, and/or intermediate results discussed in the method 200can be stored, displayed and/or outputted to another device as requiredfor a particular application. Furthermore, steps or blocks in FIG. 2that recite a determining operation, or involve a decision, do notnecessarily require that both branches of the determining operation bepracticed. In other words, one of the branches of the determiningoperation can be deemed as an optional step.

FIG. 3 depicts a high level block diagram of a general purpose computersuitable for use in performing the functions described herein. Asdepicted in FIG. 3, the system 300 comprises a processor element 302(e.g., a CPU), a memory 304, e.g., random access memory (RAM) and/orread only memory (ROM), a module 305 for providing a local classifierfor a network, and various input/output devices 306 (e.g., networkinterface cards, such as 10, 100, or Gigabit Ethernet NIC cards, FibreChannel Host Bus Adapters, Infiniband adapters, storage devices,including but not limited to, a tape drive, a floppy drive, a hard diskdrive or a compact disk drive, a receiver, a transmitter, a speaker, adisplay, a speech synthesizer, an output port, and a user input device(such as a keyboard, a keypad, a mouse, and the like)).

It should be noted that the present invention can be implemented insoftware and/or in a combination of software and hardware, or entirelyin hardware, e.g., using application specific integrated circuits(ASIC), a general purpose computer or any other hardware equivalents. Inone embodiment, the present module or process 305 for providing a localclassifier for a network can be loaded into memory 304 and executed byprocessor 302 to implement the functions as discussed above. As such,the present method 305 for providing a local classifier for a network(including associated data structures) of the present invention can bestored on a computer readable medium, e.g., RAM memory, magnetic oroptical drive or diskette and the like.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method for processing a query, comprising:receiving, by a processor, the query from a user; processing, by theprocessor, the query to locate a document in accordance with a searchengine having a discriminative classifier, wherein the discriminativeclassifier is trained with a plurality of artificial query examples,wherein the artificial query examples comprise simulated queriesautomatically generated from terms in the document, wherein one of thesimulated queries comprises a plurality of the terms selected from thedocument; retraining, by the processor, the discriminative classifierbased on an update to the document and based on an example derived froma log of previous searches; and presenting, by the processor, a resultof the processing to the user.
 2. The method of claim 1, furthercomprising: receiving a feedback on the result presented to the user;and retraining the discriminative classifier based on the feedback. 3.The method of claim 1, wherein the discriminative classifier comprises asupport vector machine classifier.
 4. The method of claim 1, wherein thediscriminative classifier is further trained based on the document beingwithin a class.
 5. The method of claim 1, wherein the query is a speechbased query.
 6. The method of claim 1, wherein the processing is basedon meta information.
 7. The method of claim 6, wherein the metainformation comprises a user profile.
 8. A tangible computer-readablemedium storing instructions which, when executed by a processor, causethe processor to perform operations for processing a query, theoperations comprising: receiving the query from a user; processing thequery to locate a document in accordance with a search engine having adiscriminative classifier, wherein the discriminative classifier istrained with a plurality of artificial query examples, wherein theartificial query examples comprise simulated queries automaticallygenerated from terms in the document, wherein one of the simulatedqueries comprises a plurality of the terms selected from the document;retraining the discriminative classifier based on an update to thedocument and based on an example derived from a log of previoussearches;and presenting a result of the processing to the user.
 9. Thetangible computer-readable medium of claim 8, further comprising:receiving a feedback on the result presented to the user; and retrainingthe discriminative classifier based on the feedback.
 10. The tangiblecomputer-readable medium of claim 8, wherein the discriminativeclassifier comprises a support vector machine classifier.
 11. Thetangible computer-readable medium of claim 8, wherein the discriminativeclassifier is further trained based on an example constructed from thedocument being within a class.
 12. The tangible computer-readable mediumof claim 8, wherein the query is a speech based query.
 13. The tangiblecomputer-readable medium of claim 8, wherein the processing is based onmeta information.
 14. The tangible computer-readable medium of claim 13,wherein the meta information comprises a user profile.
 15. An apparatusfor processing a query, comprising: a processor; and a computer-readablemedium storing instructions which, when executed by the processor, causethe processor to perform operations, the operations comprising:receiving the query from a user; processing the query to locate adocument in accordance with a search engine having a discriminativeclassifier, wherein the discriminative classifier is trained with aplurality of artificial query examples, wherein the artificial queryexamples comprise simulated queries automatically generated from termsin the document, wherein one of the simulated queries comprises aplurality of the terms selected from the document; retraining thediscriminative classifier based on an update to the document and basedon an example derived from a log of previous searches; and presenting aresult of the processing to the user.
 16. The apparatus of claim 15,wherein the method operations further comprise: receiving a feedback onthe result presented to the user; and retraining the discriminativeclassifier based on the feedback.
 17. The apparatus of claim 15, whereinthe discriminative classifier comprises a support vector machineclassifier.
 18. The apparatus of claim 15, wherein the discriminativeclassifier is further trained based on an example constructed from thedocument being within a class.
 19. The apparatus of claim 15, whereinthe query is a speech based query.
 20. The apparatus of claim 15,wherein the processing is based on meta information.